JP6954211B2 - Metal molding plate, painted metal molding plate and molding method - Google Patents

Description

The present invention relates to a metal molded plate, a painted metal molded plate and a molding method.

In recent years, in the fields of automobiles, aircraft, ships, building materials, home appliances, etc., design has been emphasized in order to meet the needs of users. Therefore, in particular, the shape of the exterior member tends to be complicated.

For example, in Patent Document 1, the aluminum alloy plate is installed in a mold so that the angle between the rolling direction of the aluminum alloy plate and the maximum molding direction in the molding process is within ± 30 °. A method for forming an aluminum alloy plate to be formed is disclosed. Patent Document 1 discloses that the generation of rigging marks during molding can be suppressed by this molding method.

Japanese Unexamined Patent Publication No. 2012-36421

However, in order to form a metal molded plate having a complicated shape from a metal plate as an exterior member, it is necessary to give a large strain to the metal plate. On the other hand, there is a problem that fine irregularities are likely to occur on the surface of the metal molded plate as the amount of processing increases, and the surface becomes rough and the appearance is spoiled.
In particular, when a metal molded plate having a ridgeline portion having a small radius of curvature on the design surface is molded by molding in order to enhance the design, unevenness develops on the convex side surface of the ridgeline portion, resulting in surface roughness and appearance. It is easy to spoil the aesthetics.

Therefore, an object of the present invention is to provide a metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridge line portion is suppressed.
Another object of the present invention is to provide a coated metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridge line portion is suppressed.
Another object of the present invention is to provide a molding method for obtaining a metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridge line portion is suppressed.

The above problem is solved by the following means. That is,

<1>
A metal molded plate having a ridge on the design surface and having a radius of curvature of 5 mm or less on the concave surface of the ridge in a cross section perpendicular to the extending direction of the ridge at the minimum thickness of the ridge. There,
The average aspect ratio of the crystal grains on the surface of the design surface where the plate thickness is maximum is 2.0 or more and less than 3.0.
The angle between the direction orthogonal to the extending direction of the ridge and the most frequent direction of the minor axis of the crystal grains on the convex surface of the minimum plate thickness of the ridge is within ± 15 °.
A metal molded plate having an arithmetic mean surface roughness Sa of 1.0 μm or less on the convex side surface of the minimum plate thickness of the ridgeline portion.
<2>
The metal molded plate according to <1>, wherein the radius of curvature of the concave surface of the ridgeline portion in the minimum plate thickness portion of the ridgeline portion is R and the plate thickness is t, and R / t is 5 or less.
<3>
The metal molded plate according to <1> or <2>, wherein the metal molded plate is made of steel.
<4>
The metal molded plate according to <1> or <2>, wherein the metal molded plate is made of an aluminum alloy.
<5>
A coated metal having the metal molded plate according to any one of <1> to <4> and a coating layer provided on at least the convex side surface of the ridgeline portion of the surface of the metal molded plate. Molded plate.
<6>
A metal plate having an average aspect ratio of crystal grains on the surface of 2.0 or more and less than 3.0 is press-molded, and the design surface has a ridgeline portion, and the ridgeline portion extends in the minimum plate thickness portion of the ridgeline portion. A molding method for obtaining a metal molded plate having a radius of curvature of 5 mm or less on the concave surface of the ridgeline portion in a cross section perpendicular to the direction.
A step of specifying the most frequent direction of the minor axis of the crystal grains on the surface of the metal plate, and
When the metal plate is press-molded, a step of specifying a direction orthogonal to the extending direction of the ridgeline portion in the minimum plate thickness portion of the ridgeline portion, and
A step of blanking the metal plate so that the angle formed by the direction orthogonal to the extending direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains is within ± 15 °.
The process of performing press molding with the angle within ± 15 ° on the blanked metal plate, and
Molding method having.
<7>
The molding method according to <6>, wherein the metal plate is made of steel.
<8>
The molding method according to <6>, wherein the metal plate is made of an aluminum alloy.

According to the present invention, it is possible to provide a metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridge line portion is suppressed.
According to the present invention, it is possible to provide a coated metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridge line portion is suppressed.
According to the present invention, it is possible to provide a molding method for obtaining a metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridge line portion is suppressed.

It is a schematic perspective view which shows an example of the metal molded plate which concerns on this embodiment. It is an enlarged schematic cross-sectional view which shows an example of the plate thickness minimum part of the ridge line part of the metal molded plate which concerns on this embodiment. It is a schematic perspective view which shows an example of the coated metal molded plate which concerns on this embodiment. It is a schematic diagram for demonstrating the molding method which concerns on this Embodiment. It is a schematic diagram for demonstrating the molding method which concerns on this Embodiment. It is a schematic diagram for demonstrating the molding method which concerns on this Embodiment.

Hereinafter, embodiments that are an example of the present invention will be described.
In this specification, the same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.
Further, the "design surface" refers to a surface that is exposed to the outside and can be an object of aesthetics among the surfaces constituting the metal molded plate.
Further, the "extending direction of the ridgeline portion at the minimum plate thickness portion of the ridgeline portion" means the direction in which the ridgeline portion extends at the minimum plate thickness portion of the ridgeline portion when the design surface having the ridgeline portion is viewed in a plan view. .. For example, when the minimum plate thickness portion of the ridge line portion has a portion where the apex of the ridge line portion draws a straight line, the "extending direction of the ridge line portion at the minimum plate thickness portion of the ridge line portion" means the direction in which the straight line extends. do. On the other hand, when the minimum plate thickness of the ridge is located at the position where the apex of the ridge draws a curve, the "extending direction of the ridge at the minimum thickness of the ridge" is the plate of the ridge with respect to the curve. It means the direction in which the tangent line extends at the minimum thickness.
Further, the "orthogonal direction of the ridgeline portion with respect to the extending direction" is also referred to as "orthogonal direction of the ridgeline portion".

In the molding method according to the present embodiment, a metal plate having an average aspect ratio of crystal grains on the surface of 2.0 or more and less than 3.0 is press-molded, has a ridge line portion on the design surface, and has a minimum plate thickness portion of the ridge line portion. This is a molding method for obtaining a metal molded plate having a radius of curvature of 5 mm or less on the concave surface of the ridgeline portion in a cross section perpendicular to the extending direction of the ridgeline portion.

The molding method according to the present embodiment includes a step of specifying the most frequent direction of the minor axis of the crystal grains on the surface of the metal plate (first step) and a plate thickness of the ridgeline portion when the metal plate is press-molded. The angle between the step of specifying the direction orthogonal to the extending direction of the ridge at the minimum part (second step) and the direction orthogonal to the extending direction of the ridge and the most frequent direction of the minor axis of the crystal grain is ± 15 °. A step of blanking the metal plate so as to be within ± 15 (third step) and a step of performing press forming with respect to the blanked metal plate so that the angle is within ± 15 ° (fourth step). And have.

Here, for example, when press molding is performed on a metal plate using a punch having a ridge line portion on the top surface, a metal molded plate having a ridge line portion on the design surface can be obtained.

However, when the ridge line portion having a small radius of curvature of the cross section is press-formed in order to enhance the design, the equivalent plastic strain (hereinafter, also referred to as “working amount”) of the ridge line portion becomes large.
Specifically, when press molding is performed in which the radius of curvature of the concave surface of the ridgeline portion in the orthogonal cross section of the ridgeline portion is 5 mm or less at the minimum plate thickness of the ridgeline portion, the equivalent plastic strain of the ridgeline portion increases. ..
In a metal molded plate having such a ridge portion having a small radius of curvature, surface roughness appears on the convex side surface of the ridge portion. In particular, among the ridgeline portions, the plate thickness minimum portion of the ridgeline portion has a large equivalent plastic strain, and surface roughness appears remarkably on the convex side surface of the ridgeline portion.

On the other hand, in the molding method according to the present embodiment, by going through the above steps, a metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridgeline portion is suppressed can be obtained. Then, the molding method according to the present embodiment was found based on the following findings.

The inventors focused on the shape of the crystal grains on the surface of the metal plate to be molded, and examined the relationship between the shape of the crystal grains and the surface roughness of the convex side surface of the ridgeline portion. As a result, the inventors obtained the following findings.

When the crystal grains on the surface of the metal plate have an elongated shape (that is, when the average aspect ratio of the crystal grains on the surface of the metal plate is 2.0 or more and less than 3.0), the major axis of the crystal grains When the direction and the direction of the main strain in the plane at the time of press molding match, surface roughness is likely to occur. It is considered that this is because the length of the crystal grains along the main strain direction is long (that is, the apparent average crystal grain size along the main strain direction is large), the crystal grains are deformed, and unevenness develops.

On the other hand, when the minor axis direction of the crystal grains and the main strain direction in the plane at the time of press molding match, surface roughness is less likely to occur. It is considered that this is because the length of the crystal grains along the main strain direction is short (that is, the apparent average crystal grain size along the main strain direction is small), and the crystal grains are less likely to be deformed.

Here, when a metal molding plate having a ridge line portion on the design surface is press-molded, the metal plate having the ridge line portion undergoes plane strain tensile deformation to form the ridge line portion. That is, the direction orthogonal to the ridgeline portion is the main strain direction.

Therefore, when the metal plate was press-formed so that the angle formed by the orthogonal direction of the ridge line and the most frequent direction of the minor axis of the crystal grains was within ± 15 °, the press molding was performed with the minor axis direction of the crystal grains. The frequency at which the main strain directions in the plane coincide with each other increases, and surface roughness on the surface of the convex portion of the ridgeline portion is less likely to occur.

In order to realize this press molding, the direction perpendicular to the ridge line portion at the minimum plate thickness of the ridge line portion is specified as well as the most frequent direction of the minor axis of the crystal grains on the surface of the metal plate. do. Then, the metal plate is blanked so that the angle formed by the orthogonal direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grain is within ± 15 °.
Then, if the blanked metal plate is press-molded so that the angle is within ± 15 °, the ridgeline is formed even if the ridgeline portion having a small radius of curvature of the cross section is press-molded in order to enhance the design. The surface roughness of the convex surface of the portion is suppressed.

From the above findings, it was found that the molding method according to the present embodiment is a molding method in which the occurrence of surface roughness on the surface of the convex portion of the ridgeline portion is suppressed.

Hereinafter, the details of the molding method according to the present embodiment will be described with reference to the drawings.

<Metal molded plate>
First, a metal molded plate obtained by the molding method according to the present embodiment (hereinafter referred to as "metal molded plate according to the present embodiment") will be described.

As shown in FIG. 1, the metal-molded plate 10 according to the present embodiment is a metal-molded plate having a ridgeline portion 12 on a bulging portion 13 which is a part or all of the design surface 11. Specifically, for example, in the metal molded plate 10, the top plate portion 14 having the ridge line portion 12, the vertical wall portion 16 adjacent to the top plate portion 14 in the periphery, and the flange 18 adjacent to the periphery in the vertical wall portion 16 It is a molded plate on the substantially hat side having and. That is, the bulging portion 13 is composed of a top plate portion 14 and a vertical wall portion 16. The flange 18 may be partially or completely removed.

The shape of the metal molded plate 10 is not limited to the above configuration as long as the plate surface has the ridge line portion 12, and various shapes (dome shape, etc.) according to the purpose can be adopted.

The ridge line portion 12 is provided linearly on the top plate portion 14 in a plan view of the metal molded plate 10. Further, the ridge line portion 12 is provided in a streamlined shape curved in a convex shape in a side view of the metal molding plate 10 viewed from the direction orthogonal to the ridge line portion 12.

Here, the ridge line portion 12 is arranged at a position separated from the edge of the metal molded plate 10 (for example, the edge of the flange 18A on the orthogonal direction of the ridge line portion 12) by 10 mm or more. That is, the ridge line portion 12 is provided inside, for example, the shoulder portion 14A (or the vertical wall portion 16A) along the extending direction of the ridge line portion 12 which is the boundary between the top plate portion 14 and the vertical wall portion 16. There is. The ridge line portion 12 may pass through the shoulder portion 14B (or the vertical wall portion 16B) intersecting the extending direction of the ridge line portion 12 and extend to the flange 18B on the extending direction of the ridge line portion 12.

The ridge line portion 12 is not limited to the above aspect, and may be linear or streamlined in a plan view. Further, in the side view, the ridge line portion 12 may be linear or streamlined.

In the ridge line portion 12, the radius of curvature of the concave surface of the ridge line portion 12 in the orthogonal cross section of the ridge line portion 12 in the minimum plate thickness portion 12A of the ridge line portion 12 is 5 mm or less (4 mm or less from the viewpoint of design). (See FIG. 2: R1 in the figure indicates the radius of curvature). However, from the viewpoint of surface roughness that cannot be suppressed on the convex side surface of the ridge line portion 12, the lower limit value of the radius of curvature is preferably 1 mm or more.

Here, the radius of curvature of the minimum plate thickness portion 12A of the ridge line portion 12 and the minimum plate thickness portion 12A of the ridge line portion 12 is measured as follows. First, the three-dimensional shape on the concave surface of the ridge line portion 12 is measured by a three-dimensional shape measuring device. Next, a computer CAD software (for example, 3DCAD Solidworks, etc.) is used to continuously acquire the orthogonal cross-sections of the ridgeline portion 12 along the parallel direction of the ridgeline portion 12, and the portion of the ridgeline portion 12 having the smallest plate thickness is obtained. Identify. This specific location is defined as the minimum plate thickness portion 12A of the ridgeline portion 12. Then, the radius of curvature of the specific portion is defined as the radius of curvature of the ridgeline portion 12 at the minimum plate thickness portion 12A.

The average aspect ratio of the crystal grains on the surface of the design surface 11 where the plate thickness is maximum is 2.0 or more and less than 3.0 (preferably 2.15 or more and less than 2.9).

The plate thickness of the portion of the design surface 11 where the plate thickness is maximum can be regarded as the plate thickness of the metal plate before press molding.
That is, the metal molded plate 10 can be regarded as a molded plate obtained by press-molding a metal plate having an average aspect ratio of crystal grains on the surface of 2.0 or more and less than 3.0.

The angle formed by the orthogonal direction of the ridge line portion 12 and the most frequent direction of the minor axis of the crystal grains on the convex side surface of the minimum plate thickness portion 12A of the ridge line portion 12 is within ± 15 ° (preferably within ± 10 °). ing.
That is, the metal molded plate 10 is formed so that the angle formed by the orthogonal direction of the ridge line portion 12 and the most frequent direction of the minor axis of the crystal grains in the minimum plate thickness portion 12A of the ridge line portion 12 is within ± 15 °. Can be regarded as a press-molded plate.
In FIG. 1, D2 indicates the orthogonal direction of the ridge line portion 12.

Here, the average aspect ratio of the crystal grains and the most frequent direction of the minor axis of the crystal grains on the surface of the metal molded plate 10 are measured by the following methods.
A sample having a surface (hereinafter, also referred to as an “observation surface”) of the metal molded plate 10 to be measured is collected.
Next, the observation surface of the sample is polished and tital-etched to corrode and develop the grain boundaries of the observation surface.
Next, an optical microscope is used to observe a 200 μm × 200 μm square region of the observation surface of the sample at a magnification of 500.
Next, in the observed crystal grains, the maximum length is defined as the major axis length, and the maximum length along the direction orthogonal to the major axis is defined as the minor axis length. The aspect ratio (= major axis length / minor axis length) is calculated from the measured major axis length and minor axis length. Then, the arithmetic mean of each aspect ratio of the crystal grains observed on the observation surface is defined as the average aspect ratio.

In addition, each minor axis direction of the crystal grains observed on the observation surface is obtained. Then, the minor axis direction of the most abundant crystal grains is defined as the most frequent direction of the minor axis of the crystal grains.

The arithmetic mean surface roughness Sa on the convex side surface of the minimum plate thickness portion 12A of the ridge line portion 12 is 1.0 μm or less (preferably 0.8 μm or less). That is, the surface roughness of the convex side surface of the ridge line portion 12 is reduced.

The arithmetic mean surface roughness Sa of the convex side surface of the ridge line portion 12 is measured according to ISO-25178. Specifically, the arithmetic mean surface roughness Sa is centered on the convex side apex of the ridge line portion 12 and is "2 mm along the extending direction of the ridge line portion 12 in the minimum plate thickness portion 12A of the ridge line portion 12" × " A four-sided region of "2 mm along the orthogonal direction of the ridgeline portion 12 in the minimum plate thickness portion 12A of the ridgeline portion 12" (see FIGS. 1 and 2: T in the figure indicates a four-sided region, and S is a convex side of the ridgeline portion 12. (Ridge) is the arithmetic mean value measured at three points.
The surface shape cutoff conditions are S-filter = 0.8 μm and L-filter = 2.5 mm.

The metal molded plate 10 according to the present embodiment described above has a ridge line portion at the minimum plate thickness of the ridge line portion 12 with respect to a metal plate having an average aspect ratio of crystal grains on the surface of 2.0 or more and less than 3.0. The radius of curvature of the concave surface of 12 and the angle formed by the orthogonal direction of the ridge 12 on the convex surface of the minimum plate thickness of the ridge and the most frequent direction of the minor axis of the crystal grains are in the above range. It is a molded metal molded plate. Even if the metal molded plate 10 is press-molded under the above conditions, the arithmetic average surface roughness Sa on the convex side surface of the minimum plate thickness portion 12A of the ridge line portion 12 is 1.0 μm or less. That is, it is a metal molded plate in which the occurrence of surface roughness on the surface of the convex portion of the ridgeline portion is suppressed.

Hereinafter, a preferred embodiment of the metal molded plate 10 according to the present embodiment will be described.

The metal molded plate 10 has an R / t of 5 when the radius of curvature of the concave surface of the ridgeline portion 12 in the minimum plate thickness portion 12A of the ridgeline portion 12 is R (mm) and the plate thickness is t (mm). The following is preferable.

This is because when the R / t of the metal molded plate 10 is larger than 5, the equivalent plastic strain applied to the surface is small and the surface roughness is less likely to become apparent. The lower limit of R / t is 1. When R / t is less than 1, the equivalent plastic strain applied to the surface is large and bending cracks may occur. From the viewpoint of crack suppression, for example, it is set to 1 or more.

The metal molded plate 10 is typically a metal molded plate having a bcc structure (body-centered cubic lattice structure). Examples of the metal molded plate having a bcc structure include metal molded plates such as α-Fe, Li, Na, K, β-Ti, V, Cr, Ta, and W. Among these, steel metal molded plates (ferritic steel sheets, bainite steel sheets having a bainite single-phase structure, metal molded plates such as martensite steel sheets having a martensite single-phase structure) are preferable, and ferritic steel sheets are more preferable. The ferritic steel sheet includes a steel sheet in which martensite, bainite and the like are present (DP steel sheet) in addition to a steel sheet having a ferrite content of 100% in a metal structure.

Here, the ferrite fraction of the steel metal molded plate is preferably 70% or more, more preferably 80% or more. When the ferrite fraction of the metal structure is 70% or more, the development of unevenness is less likely to occur due to the difference in hardness between the hard phase and the soft ferrite ferrite. As a result, the occurrence of surface roughness of the metal molded plate is suppressed.
The ferrite fraction can be measured by the following method. After polishing the surface of the steel metal molded plate, it is immersed in a nital solution to reveal the ferrite structure, and a microstructure photograph is taken with an optical microscope. Then, the area of the ferrite structure is calculated with respect to the area of the entire area of the structure photograph.

Among the metal molded plates 10, the steel metal molded plates have a mass% of C: 0.00050 to 0.0080%, Si: 0.005 to 1.0%, Mn: 1.50% or less, P: 0.100% or less, S: 0.010% or less, Al: 0.00050 to 0.10%, N: 0.0040% or less, Ti: 0.0010 to 0.10%, Nb: 0. A molded plate containing 0010 to 0.10% and B: 0 to 0.0030% and having a chemical composition in which the balance is Fe and impurities can be exemplified.

The metal molded plate 10 may be a metal molded plate made of metal such as γ-Fe (austenite-based stainless steel), aluminum, aluminum alloy titanium alloy, magnesium alloy, copper, nickel, brass, and white copper. Among these, the metal molded plate 10 is preferably a metal plate having an fcc structure (body-centered cubic lattice structure) (particularly, a metal molded plate made of an aluminum alloy).

<Painted metal molded plate>
Hereinafter, a painted metal molded plate having a surface coated on the surface of the metal molded plate according to the present embodiment (hereinafter referred to as “painted metal molded plate according to the present embodiment”) will be described.

The coated metal molded plate 100 according to the present embodiment is, for example, as shown in FIG. 3, among the surfaces of the metal molded plate 10 according to the present embodiment and the metal molded plate 10, at least the convex side surface of the ridge line portion 12. It has a coating layer 20 provided in the above.

The method for forming the coating layer 20 is not particularly limited, and examples thereof include well-known coating treatments such as electrodeposition coating treatment.
The coating layer 20 may be a single layer or a plurality of layers (for example, a plurality of layers having an undercoat coating layer, an intermediate coating layer, a topcoat coating layer, and the like).

Since the painted metal molded plate 100 according to the present embodiment is a painted product in which the surface of the metal molded plate 10 according to the present embodiment is painted, similarly, the occurrence of surface roughness on the convex surface of the ridgeline portion is suppressed. It is a painted metal molded plate.

<Molding method>
Next, the molding method according to this embodiment will be described.
The molding method according to the present embodiment is a molding method for obtaining a metal molded plate by press molding a metal plate having an average aspect ratio of crystal grains on the surface of 2.0 or more and less than 3.0.

(First step)
In the first step, the most frequent direction of the minor axis of the crystal grains on the surface of the metal plate having the average aspect ratio of the crystal grains on the surface of 2.0 or more and less than 3.0 is specified (see FIG. 4).
In FIG. 4, St indicates a metal plate, Cr indicates a crystal grain, and D1 indicates the most frequent direction of the minor axis of the crystal grain. (A) in FIG. 4 is a partially enlarged view (schematic view of an SEM photograph) of the surface of a metal plate.

Specifically, with respect to the metal plate to be molded, the average aspect ratio of the crystal grains on the surface and the most frequent direction of the minor axis of the crystal grains are measured.

The average aspect ratio of the crystal grains and the most frequent direction of the minor axis of the crystal grains in the metal molded plate are measured by the same method as that for the metal molded plate. However, the sample to be collected shall be a sample having a surface (observation surface) 20 mm or more away from the edge of the metal plate.

(2nd to 3rd process)
In the second step, when the metal plate is press-molded, the orthogonal direction of the ridge line portion at the minimum plate thickness portion of the ridge line portion is specified. Then, in the third step, the metal plate is blanked so that the angle formed by the orthogonal direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains is within ± 15 °.

Specifically, for example, in a region where a metal plate is blanked by a molding simulation, when the blanked metal plate is press-molded, a region that becomes a ridge line portion, a region that becomes a minimum plate thickness portion of the ridge line portion, and a ridge line. Specify the orthogonal direction of the ridgeline portion at the minimum plate thickness portion of the portion.
After identifying these, the region for blanking the metal plate is determined so that the angle formed by the orthogonal direction of the ridge line and the most frequent direction of the minor axis of the crystal grains is within ± 15 ° (see FIG. 5). ). Then, the metal plate is blanked (see FIG. 6).

In FIGS. 5 to 6, St is a metal plate, St1 is a region for blanking a metal plate, St2 is a blanked metal plate, P1 is a region serving as a ridgeline portion, and P2 is a minimum plate thickness portion of the ridgeline portion. In the region, D1 indicates the most frequent direction of the minor axis of the crystal grain, and D2 indicates the orthogonal direction of the ridgeline portion at the minimum plate thickness of the ridgeline portion.

(Fourth step)
In the fourth step, press molding is performed on the blanked metal plate so that the angle formed by the orthogonal direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains is within ± 15 °.
The type of press molding is not particularly limited, and may be any molding method (for example, overhang molding, draw overhang molding, etc.) that can obtain a metal molded plate having a ridge line portion on the design surface.
By this molding, the desired metal molded plate is obtained (see FIG. 1).

In the molding method according to the present embodiment described above, press molding is performed in which the angle formed by the orthogonal direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains is within ± 15 ° with respect to the blanked metal plate. Therefore, even if the ridgeline portion having a small radius of curvature of the cross section is press-molded in order to enhance the design, the surface of the convex portion surface of the ridgeline portion is roughened.
Therefore, the molding method according to the present embodiment is a molding method in which the occurrence of surface roughness on the surface of the convex portion of the ridgeline portion is suppressed.

Hereinafter, the present invention will be described in more detail with reference to examples. However, each of these examples does not limit the present invention.

(Example 1)
C: 0.038, Si: 0.012, Mn: 0.19, P: 0.020, S: 0.003, Al: 0.041, N: 0.003, Ti: 0.001, Nb: A steel sheet having a thickness of 0.75 mm was prepared, which contained 0.001 and B: 0.0001, and the balance was composed of Fe and impurities. The "average aspect ratio" of the surface of the steel sheet was 2.17, and the "most frequent direction of the minor axis of the crystal grains" with respect to the rolling direction of the steel sheet was 40 °.

Next, the rectangular steel plate was blanked in order to form the molded plate having the shape shown in FIG. However, when the molded plate having the shape shown in FIG. 1 is formed in advance, in the region where the steel plate is blanked by the forming simulation, when the blanked steel plate is press-formed, the region becomes the ridge line portion and the plate of the ridge line portion. The region to be the minimum thickness and the orthogonal direction of the ridge in the minimum thickness of the ridge were specified. Then, a region for blanking the steel sheet is determined so that the angle formed by the orthogonal direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains is 0 °, and the steel sheet having a plate thickness t of 0.6 mm is formed. I ranked.

Then, press molding was carried out so that the radius of curvature R of the concave surface of the ridge line portion 12 at the minimum plate thickness portion 12A of the ridge line portion 12 was 3 mm, and a molded plate having the shape shown in FIG. 1 was obtained.

(Examples 2 to 6, Comparative Examples 1 to 5)
A steel plate before blanking (steel plate before blanking) was prepared for the "average aspect ratio" and "most frequent direction of the minor axis of crystal grains" shown in Table 1.
Next, the region for blanking the steel sheet was determined so that the angle formed by the orthogonal direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains was the angle shown in Table 1, and the steel sheet was blanked.
Then, the angle formed by the orthogonal direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains with respect to the blanked steel plate, and the concave side surface of the ridge line portion 12 in the plate thickness minimum portion 12A of the ridge line portion 12 Press molding was carried out in which the radius of curvature R and the plate thickness t were the values shown in Table 1.
As described above, a molded plate having the shape shown in FIG. 1 was obtained in the same manner as in Example 1 except for these conditions.

(evaluation)
With respect to the obtained steel molded plate, the arithmetic mean surface roughness Sa on the convex side surface of the minimum plate thickness of the ridgeline portion was measured according to the method described above.

The results are shown in Table 1.

From the above results, the steel molded plate obtained by the molding method of the example has a lower arithmetic mean surface roughness Sa of the convex side surface of the ridge line portion at the minimum plate thickness portion of the ridge line portion than in Comparative Examples 1 to 5. It can be seen that the steel molded plate is suppressed from the occurrence of surface roughness on the surface of the convex portion of the ridgeline portion.

10 Metal molded plate 11 Design surface 11A Edge of metal plate 11B Edge of metal plate 12 Ridge of metal molded plate 12A Minimum thickness of ridge of metal molded plate 14 Top plate of metal molded plate 14A Shoulder of metal molded plate along the extending direction 14B Shoulder of metal molded plate intersecting with extending direction of ridge 16 16 Vertical wall of metal molded plate 16A Vertical of metal molded plate along extending direction of ridge Wall 16B Vertical wall of metal molded plate that intersects the extending direction of the ridge 18 18 Flange of metal molded plate 18A Metal molding on the orthogonal direction of the ridge 18B Metal molding on the extending direction of the ridge Plate flange

Claims (8)

A metal molded plate having a ridge on the design surface and having a radius of curvature of 5 mm or less on the concave surface of the ridge in a cross section perpendicular to the extending direction of the ridge at the minimum thickness of the ridge. There,
The average aspect ratio of the crystal grains on the surface of the design surface where the plate thickness is maximum is 2.0 or more and less than 3.0.
The angle between the direction orthogonal to the extending direction of the ridge and the most frequent direction of the minor axis of the crystal grains on the convex surface of the minimum plate thickness of the ridge is within ± 15 °.
A metal molded plate having an arithmetic mean surface roughness Sa of 1.0 μm or less on the convex side surface of the minimum plate thickness of the ridgeline portion. The metal molded plate according to claim 1, wherein the radius of curvature of the concave surface of the ridgeline portion in the minimum plate thickness portion of the ridgeline portion is R and the plate thickness is t, and the R / t is 5 or less. The metal molded plate according to claim 1 or 2, wherein the metal molded plate is made of steel. The metal molded plate according to claim 1 or 2, wherein the metal molded plate is made of an aluminum alloy. A coated metal having the metal molded plate according to any one of claims 1 to 4, and a coating layer provided on at least the convex side surface of the ridgeline portion of the surface of the metal molded plate. Molded plate. A metal plate having an average aspect ratio of crystal grains on the surface of 2.0 or more and less than 3.0 is press-molded, and the design surface has a ridgeline portion, and the ridgeline portion extends in the minimum plate thickness portion of the ridgeline portion. A molding method for obtaining a metal molded plate having a radius of curvature of 5 mm or less on the concave surface of the ridgeline portion in a cross section perpendicular to the direction.
A step of specifying the most frequent direction of the minor axis of the crystal grains on the surface of the metal plate, and
When the metal plate is press-molded, a step of specifying a direction orthogonal to the extending direction of the ridgeline portion in the minimum plate thickness portion of the ridgeline portion, and
A step of blanking the metal plate so that the angle formed by the direction orthogonal to the extending direction of the ridge line portion and the most frequent direction of the minor axis of the crystal grains is within ± 15 °.
The process of performing press molding with the angle within ± 15 ° on the blanked metal plate, and
Molding method having. The molding method according to claim 6, wherein the metal plate is made of steel. The molding method according to claim 6, wherein the metal plate is made of an aluminum alloy.

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